Phosphorus-containing polyesters

ABSTRACT

PHOSPHOROUS-CONTAINING POLYESTER MOLDING RESIN COMPOSITIONS HAVING IMPROVED FLAME RETARDANT PROPERTIES WHEREIN SAID POLYESTER COMPOSITIONS COMPRISE MELT BLENDS OF A REINFORCING AGENT, A SYNTHETIC LINEAR POLYPROPYLENE TEREPHTHALATE OR POLYBUTYLENE TEREPHTHALATE, AND UP TO ABOUT 30 PERCENT, BASED ON THE WEIGHT OF POLYESTER, OF A POLYPHOSPHONATE OR POLY(PHOSPHONATE-PHOSPHATE) HAVING A THE FOLLOWING GENERAL FORMULA.   R1-((-P(=O)(-R)-O-AR1-Z1-)Q-(-P(=O)(-OR3)-O-AR2-Z1-)R)X-Z2   WHEREIN R1 IS A MONOVALENT RADICAL HAVING UP TO ABOUT 20 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF ALKOXY, ARYLOXY, HYDROXY, HALOALKOXY, HALOARYLOXY, HYDROXYALKOXY, AND HYDROXYARYLOXY; R2 IS A MONOVALENT RADICAL HAVING UP TO 20 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL, ARYL, HALOALKYL, AND HALOARYL; R3 IS A MONOVALENT RADICAL HAVING UP TO 20 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF ALKYL, ARYL, HALOALKYL AND HALOARYL; AR1 AND AR2 ARE DIVALENT RADICALS EACH HAVING UP TO ABOUT 20 CARBON ATOMS INDEPENDENTLY SELECTED FROM THE GROUP CONSISTING OF ARYLENE AND HALOARYLENE; Z1 IS A DIVALENT RADICAL SELECTED FROM THE GROUP CONSISTING OF ALKYLENE, ARYLENE, HALOALKYLENE, HALOARYLENE, OXY, THIO, AND SULFONYL, Z2 IS EITHER HYDROGEN OR   -P(=O)(-R2)-R1   Q IS AN INTEGER OF AT LEAST 1; R IS 0 OR AN INTEGER OF AT LEAST 1; X IS GREATER THAN 1. THE MOST PREFERRED POLYPHOSPHONATE IS POLY(M-PHENYLENE PHENYLPHOSPHONATE). THE MOST PREFERRED COPOLYMER IS POLY(M-PHENYLENE PHENYLPHOSPHATE)Q(M-PHENYLENE PHENYLPHOSPHONATE)R) WHERE Q/R IS GREATER THAN 3.

States Patent 3,830,771 PHOSPHORUS-CONTAINING POLYESTERS Stuart LyleCohen, Charlotte, N.C., and Robert William Stackman, Morristown, N.J.;said Stackman assignor to Celanese Corporation, New York, N.Y.; saidCohen assignor to Fiber Industries, Inc.

No Drawing. Continuation-impart of application Ser. No.

51,019, June 29, 1970. This application June 25, 1971,

Ser. No. 156,949 The portion of the term of the patent subsequent toJune 25, 1991, has been disclaimed Int. Cl. C08g 51/02; C09k 3/28 U.S.Cl. 260-40 R Claims ABSTRACT OF THE DISCLOSURE wherein R is a monovalentradical having up to about 20 carbon atoms selected from the groupconsisting of alkoxy, aryloxy, hydroxy, haloalkoxy, haloaryloxy,hydroxyalkoxy, and hydroxyaryloxy; R is a monovalent radical having upto 20 carbon atoms selected from the group consisting of hydrogen,alkyl, aryl, haloalkyl, and haloaryl; R is a monovalent radical havingup to 20 carbon atoms selected from the group consisting of alkyl, aryl,haloalkyl and haloaryl; Ar and Ar are divalent radicals each having upto about 20 carbon atoms independently selected from the groupconsisting of arylene and haloarylene; Z is a divalent radical selectedfrom .the group consisting of alkylene, arylene, haloal'kylene,

haloarylene, oxy, thio, and sulfonyl, Z is either hydrogen or i li q isan integer of at least 1; r is 0 or an integer of at least 1; x isgreater than 1. The most preferred polyphosphonate is p0ly(m-phenylenephenylphosphonate). The most preferred copolymer is poly[(m-phenylenephenylphosphonate) (m-phenylene phenylphosphonateh] where q/ r isgreater than 3.

This application is a continuation-impart of Application Ser. No. 51,019filed June 29, 1970.

BACKGROUND OF THE INVENTION This invention relates to reinforcedsynthetic linear polyester molding resin compositions containingphosphorus. More particularly, the invention relates to meltblends ofreinforcing agents, synthetic linear polypropylene terephthalate orpolybutylene terephthalate and polyphosphonates orpoly(phosphonate-phosphate) copolymers, which impart flame retardantproperties to said compositions.

Recent investigations with reinforced polypropylene terephthalate andpolybutylene terephthalate molding resins have found them to besurprisingly superior to similarly reinforced polyethylene terephthalatein many important processing and performance characteristics. Forexample, polypropylene terephthalate and polyice butylene terephthalatecan be molded and otherwise processed at lower temperatures, have ashorter cycle time in the mold and do not require, as does thepolyethylene terephthalate, the presence of either a nucleating agent toinduce crystallinity or a mold-release agent. Furthermore, reinforcedpolypropylene terephthalate and polybutylene terephthalate moldingresins have correspondingly higher tensile strength, lower waterabsorption and better creep (fiexural) properties than does similarlyreinforced polyethylene terephthalate. As a direct result, thesepolypropylene terephthalate and polybutylene terephthalate moldingresins which were first disclosed, along with polyethylene terephthalatein U.S. Pat. 2,- 465,319 issued to Whinfield and Dickson, have beenfound to solve processing problems long associated with polyethyleneterephthalate and believed, by those skilled in the art, to be equallyassociated with all polyalkylene terephthalates. Equally as significantthese molding resins present a noticeably improved balance ofperformance properties which those skilled in the art did not believe toexist, witness the extensive use of polyethylene ter ephthalate moldingresins to the almost total exclusion of other polyalkyleneterephthalates. Consequently, the superior processing requirements andphysical properties of polypropylene terephthalate and polybutyleneterephthalate molding resins makes them more commercially desirable,with a wider area of applicability than polyethylene terephthalate.

These molding resins do, however, have one considerable drawback-theyare flammable. Quite significantly, the presence of many importantreinforcing agents, such as glass, enhances rather than deters theburning rate of these molding resins. Since the reinforcing agents havea direct effect on the desirable physical-mechanical prop erties ofthese molding resins, several commercially advantageous applications areprecluded.

This invention is concerned with molding resins, i.e., resins useful forproducing articles of substantial thickness, -i.e., thicknesses greaterthan 10 mils. Articles which may be produced are construction panels,refrigerator doors, pipes, rods, automobile panels, sheeting, etc. Suchmolded articles do not include those which have a very small dimensionsuch as fibers and thin film. 'Ihe ditficulties to be expected whenmolding the basic reinforced polyester resin system to form articles ofsubstantial thickness are set out in U.S. 'Pat. 3,516,957. Surprisingly,it has been found that reinforced, especially glass-reinforced,polypropylene terephthalate or polybutylene terephthalate molding resinsdo not require either a nucleating agent or mold release agent, thenecessity for the incorporation of the combination of which forms thebasis of the invention claimed in that patent. Reinforced polypropyleneterephthalate and polybutylene terephthalate molding reesins are thesubject of copending U.S. Application Ser. No. 854,259, filed Aug. 29,1969.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide reinforced polyalkylene terephthalate molding resins,specifically polypropylene terephthalate and polybutylene terephthalate,with intrinsic viscosities in the range of from about 0.2 to about 1.2.deciliters per gram, having reduced burning or self-extinguishingproperties.

It is another object of this invention to provide a reinforced moldingresin composition which is capable of being used to produceflame-retardant shaped articles.

It is still another object of the present invention to provide a moldingresin composition which is capable of providing flame-retardant shapedarticles without detrimentally affecting other desirable properties ofsaid shaped articles.

These and other objects will be apparent to those skilled in the artfrom a consideration of the description and claims which follow.

In accordance with the present invention, flame-retardant polyestercompositions are obtained by melt-blending a polyphosphonate or apoly(phosphonate-phosphate) a linear synthetic polypropyleneterephthalate or polybutylene terephthalate and a reinforcing agent,wherein said polyphosphonate or poly(phosphonate-phosphate) may berepresented by the following general formula:

wherein R is a monovalent radical having up to about 20 carbon atomsselected from the group consisting of alkoxy, aryloxy, hydroxy,haloalkoxy, haloaryloxy, hydroxyalkoxy, and hydroaryloxy; R is amonovalent radical having up to 20 carbon atoms and selected from thegroup consisting of hydrogen, alkyl, aryl, haloalkyl, and haloaryl; R isa monovalent radical having up to 20 carbon atoms and selected from thegroup consisting of alkyl, aryl, haloalkyl and haloaryl; Ar and Ar aredivalent radicals each having up to about 20 carbon atoms inde pendentlyselected from the group consisting of arylene and haloarylene; Z is adivalent radical selected from the group consisting of al-kylene,arylene, haloalkylene, haloarylene, oxy, thio, and sulfonyl; Z is eitherhydrogen q is an integer of at least 1; r is or an integer of at least1; x is greater than 1. The most preferred homopolymer is apoly(m-phenylene phenylphosphonate) wherein R is a phenoxy; R is phenyl,Ar is m-phenylene, m is 1, n and p each are 0, Z is The most preferredcopolymer is the copolymer poly[(m phenylene phenylphosphonate) (mphenylene phenylphosphateh] where q/r is greater than 3. Thepoly(phosphonate-phosphate) copolymers are economi cally attractivecompared to poly-phosphonate homopolymers. In the reinforced moldingresin compositions of the invention, the polyphosphonate orpoly(phosphonatephosphate) is present in the compositions in an amountup to about 30 Weight percent, based on the weight of the polyalkyleneterephthalate. The preferred range of polyphosphonate orpoly(phosphonate-phosphate) incorporation is from about 3 Weight percentto about 15 weight percent. The reinforcing agent is present in anamount of from about 2 to about 60 weight percent based on the weight ofthe total composition, preferably from about 5 to about 40 weightpercent.

DETAILED DESCRIPTION OF THE INVENTION The base of the molding resins ofthis invention is a polyalkylene terephthalate polymer selected from thegroup consisting of polypropylene terephthalate and polybutyleneterephthalate. These polymers, Which are of the general type describedin US. Pat. No. 2,465,319 to Whinfield and Dickson, can be produced bythe reaction of a dibasic acid, such as terephthalic acid or a dialkylester of terephthalic acid (especially dimethyl terephthalate), anddiols having 3 or 4 carbon atoms. Suitable diols include1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-propanediol,1,2-butanediol, 2,3-butanediol, and the like.

In the productions of the polymers used in this invention, i.e.,polypropylene or polybutylene terephthalate,

the appropriate bis (hydro-xyalkyl) terephthalate is produced as theintermediate. The bis (hydroxyal kyl) terephthalate can be prepared byreacting the dialkyl ester of terephthalic acid in which the alkylradicals can contain from 1 to 7 carbon atoms with about two molecularproportions of the diols described above. It is preferred to use higherproportions of the diol, i.e., in excess of 1.5 moles of the diol permole of the terephthalate derivative, because by using such proportions,the initial transesterification is caused to take place more rapidly andcompletely.

The reaction for the esteri fication is conducted under conditions ofelevated temperatures and atmospheric, subatmospheric orsuperatmospheric pressure. Normally, the desired temperatures of thereaction can range from about the boiling temperature of the reactionmixture to as high as 250 C. if desired,

It is preferred that synthetic linear polyesters of the presentinvention containing moieties from 1,4-butanediol as the diol componentbe prepared in the absence of group VA catalysts. Thus it is preferredthat such polyesters be prepared in accordance with e.g., 'Examples 13and 23 of copending and commonly assigned application Ser. No. 879,618,filed on Nov. 24, 1969.

The polyphosphonate or poly(phosphonate-phosphate) may be admixed withthe polyester in any convenient and effective manner. Thepolyphosphonate is generally the more viscous of the two, and thereforemelt blending of sufficient duration is required to effect intimateadmixture.

After the polymer base is prepared, the reinforcing agents can beintimately blended by either dry blending or melt blending, blended inextruders, heated rolls or other type of mixers. If desired, thereinforcing agents can be blended with the monomers in thepolymerization reaction as long as the polymerization reaction is notaffected. Alternatively, the reinforcing agent can be added afterpolymerization and prior to extrusion. The types of reinforcing agentswhich can be used include, among othrs, glass fibers (chopped orcontinuous rovings), asbestos, cellulosic fibers, cotton fabric paper,synthetic fibers, metallic powders and the like. The amount ofreinforcing agent can range from about 2 to about 60 weight percent,preferably from about 5 to about 40 weight percent based on the totalmolding composition. Other additives for appearance and propertyimprovements can be incorporated into the molding resins of thisinvention such as colorants, plasticizers, stablizers, hardeners, andthe like.

The sequence of mixing is generally not critical. Either the reinforcingagent or polyphosphonate or poly(phosphonate-phosphate) may first beadmixed with the polyester, or both additives may :be simultaneouslyadmixed with the polyester. It is preferred, however, that because ofits viscosity, the polyphosphonate or poly(phosphonatephosphate) beadmixed with the polyester before the other additives.

Glass reinforced polybutylene terephthalate and polypropyleneterephthalate resins have important advantages over the equivalent glassreinforced polyethylene terephthalate. Compound to polyethyleneterephthalate, polybutylene terephthalate and polypropyleneterephthalate can be processed at much lower temperatures, at asignificantly lower cycle time and with a lower mold temperature. Inaddition they have noticeably higher notched Izod and tensile impact,less shrinkage and lower water absorption than does polyethyleneterephthalate. Also, the ends of the reinforcing agent, especiallyglass, do not tend to migrate to the surface, thereby rendering it ofuneven gloss or blemished. All of these improved processing and physicalcharacteristics of the glass reinforced polybutylene terephthalate andpolypropylene terephthalate resins are highly desirable and have directcommercial ramifications, when compared to equivalent glass reinforcedpolyethylene terephthalate resin.

More importantly though, these improvements in processability andphysical characteristics between polyethylene terephthalate on one handand polypropylene terephthalate and polybutylene terephthalate on theother hand are so disproportionate as to lead one to the conclusion thatpolypropylene terephthalate and polybutylene terephthalate aredifferent, at least physically, from polyethylene terephthalate. Thatis, the improvements realized by this seemingly small change in chemicalstructure are so out of proportion, relative to what would and should beexpected, as to make polypropylene terephthalate and polybutyleneterephthalate entirely distinct from and unrelated to polyethyleneterephthalate.

These new resins do, however, have one deleterios propertythey areflammable and when burning, drip a significant quantity of flamingparticles. In the hereinafter described burn test, 30 weight percentglass reinforced polybutylene terephthalate is found to burn at a rateof 2.3 inches per minute; polypropylene terephthalate burns at a similarrate. To those skilled in the art this is an unacceptable and unsafecondition, resulting in curtailed application for these otherwise highlydesirable materials.

The test procedure used involves supporting, at one end, a specimen 6inches in length by /2 inch in width in either inch or A; inchthickness, by a clamp, with the longest dimension being vertical. Abunsen burner flame, from a burner having a 3.8 inch diameter tube and ablue flame inch in height is placed under the suspended sample so thatthe bottom of the sample is inch above the top of the burner tube. Thetest flame is allowed to remain for 10 seconds, withdrawn, and theduration of flaming or glowing combustion of the specimen is noted. Ifflaming or glowing combustion of the specimen ceases Within 30 secondsafter removal of the test flame, it is again placed under the specimenfor 10 seconds immediately after flaming or glowing combustion of thespecimen stops. The burn rate is calculated as the number of inchesconsummed by both the bunsen flame and self-combustion during oneminute. According to the present description a reinforced polypropyleneterephthalate or polybutylene terephthalate is considered to havereduced burning properties if, during the above combustion conditions,the burn rate is less than 1.1 inches per minute and no dripping offlaming particles occurs.

The present invention addresses itself to the problem of theflammability of polypropylene terephthalate and polybutyleneterephthalate. More specifically, it addresses itself to the problem ofthe flammability of an intimate blend of polypropylene terephthalate orpolybutylene terephthalate with reinforcing agents because in mostinstances it was found that the presence of the reinforcing agentincreased the burning rate of the resin.

It has been found that polyphosphonates or poly (phosphonate-phosphates)when used in accordance with this invention, effectively reduce theburning properties of reinforced polypropylene terephthalate andpolybutylene terephthalate.

The polyphosphonates and poly(phoshonate-phosphate) copolymers of thepresent invention may be prepared by methods similar to those well knownin the art. Such methods include melt condensation of aromatic diolswith phenyl phosphonic dichloride (W. R. Sorenson and T. W. Campbell,Preparative Methods of Polymer Chemistry, 2nd Edition, WileyInterscience, New York, 1968, pp. 145-6), and the solutionpolymerization of aromatic diols with phosphorus chlorides. Such methodsalso include, for example, melt condensation of aromatic diols with fourparts of phenyl phosphonic dichloride and one part of phenyldichlorophosphate (see the Sorenson and Campbell reference mentionedabove).

The phosphorus-containing polymers as described hereinbefore havemolecular weights varying within a wide range. Thus, the polymers mayrange from oligomers (i.e., x is in the range of from 2 to about 4) topolymers containing up to or more repeat units (i.e., x equal to 100 ormore). When R is aryl or haloaryl it is preferred that the value of q/ rbe greater than 2, since at high levels of phosphate the polymercross-links apparently due to exchange of the phenoxy side chain withresorcinol; and it is most preferred that the value of q/ r be greaterthan 3. However, when R is alkyl or haloalkyl cross-linking is minimizedand the preferred range of q/ r is A to 4. Values of q/r less than A areundesirable since they tend to give a brown polymer, particularly athigh concentrations of the copolymer additive. It is desirable that thepolymers have a degree of polymerization of at least about 3. The termdegree of polymerization refers to the value of x and eliminates thenecessity of calculating molecular weight ranges for all polymersencompassed by the general formula described hereinbefore. Thus,depending upon the polymer and polyester employed, it may be desirableto utilize copolymers having a degree of polymerization from about 3 toabout 10. However, it may be desirable on occasion to utilize copolymershaving a degree of polymerization somewhat greater than 10, perhaps ashigh as about 100. Additionally, the polymers with R being aryl orhaloaryl may be capped by the addition of minor amounts of an alcohol orphenol to the reaction mixture. This procedure minimizesphosphorus-chlorine bonds in the resultant copolymer which tend todiscolor polyester. Further the procedure serves as a means forcontrolling molecular weight or degree of polymerization of thepolymers.

Preferably, the phosphorus-containing copolymers of the presentinvention are prepared by the reaction of one part of phenyldichlorophosphate and at least four parts of either methyl phosphonicdichloride or phenyl phosphonic dichloride with an aromatic diol such asresorcinol, hydroquinone, catechol, 4,4'-dihydroxybiphenyl,2,2-bis-(4-hydroxyphenyl)propane, and the like.

As stated hereinbefore, the flame retardant polyester compositions ofthe present invention are obtained by melt-blending up to 30 weightpercent of a polyphosphonate or poly(phosphonate-phosphate) copolymer asdefined hereinbefore with polypropylene terephthalate or polybutyleneterephthalate.

The preferred range of copolymer incorporation is from about 3 weightpercent to about 15 weight percent. The most preferred range is from 3weight percent to about 10 weight percent. The term melt-blending asused herein refers to the physical mixing of the copolymer additive withthe polyester while the latter is in a molten state. Thus, the polymermay be added to the polymerization vessel either during or afterpolymerization of the polyester. Alternatively, the polymer may be mixedor blended with polyester chip and the resultant mixture melted.Obviously, the melting step in the latter procedure may be part of theextrusion operation which provides shaped articles from said flameretardant polyester composition.

As stated hereinbefore, the flame-retardant polyester compositions ofthe present invention are obtained by melt-blending up to 30 weightpercent of a polyphosphonate or poly(phosphonate-phosphate) as definedhereinbefore with a reinforcing'agent and a synthetic linear polyesteralso defined hereinbefore. The preferred range of polyphosphonate orpoly(phosphonate-phosphate) incorporation is from about 3 weight percentto about 15 weight percent. The most preferred range is from 3 weightpercent to about 10 weight percent. The weight percent of thepolyphosphonate or poly(phosphonate-phosphate) is based on the weight ofthe polyester. The term meltblending as used herein refers to thephysical mixing of the polyphosphonate or poly(phosphonate-phosphate)additive with the polyester while the latter is in a molten state. Thus,the polyphosphonate or poly(phosphonatephosphate) may be added to thepolymerization vessel either during or after polymerization of thepolyester.

Alternatively, the polyphosphonate or poly(phosphonatephosphate) may bemixed or blended with polyester chip and the resultant mixture melted.Obviously, the melting step in the latter procedure may be part oftheextrusion operation which provides shaped articles from saidflameretardant polyester composition.

The flame-retardant polyester compositions of the present invention maybe utilized for the production of molded articles of substantialthickness by conventional methods. Such methods include injectionmolding, rotational molding, and melt-extruding.

The flame-retardant polypropylene terephthalate and polybutyleneterephthalate composition of the present invention may be utilized inthe preparation of molding compositions in pellet or powder form, whichcompositions may also incorporate ingredients such as glass, china clay,talc, etc.

The range of intrinsic viscosity of the polypropylene terephthalate andpolybutylene terephthalate should be between about 0.2 to about 1.2deciliter per gram with the preferred range being between about 0.5 toabout 1.0 deciliters per gram. Reinforcing agents may be present fromabout 2 to about 60 weight percent based on the weight of the totalcomposition, the preferred range being between about 5 to about 40weight percent. A large variety of reinforcing agents are contemplatedby the present invention such as, asbestos fibers, cellulosic fibers,cotton fabric paper, synthetic fibers, metallic powders and the like;the preferred reinforcing agent, however, is glass fiber in chopped orcontinuous roving form. The chopped glass fiber used can range inlengths from inch or shorter to A inch or longer.

The polyphosphonates or poly(phosphonate phosphates) may be incorporatedin the molding resins of the present invention in any standard manner.It is preferred, however, that they be added during the polymerizationreaction and, prior to the introduction of the reinforcing agent. Thefollowing examples demonstrate, without limiting the present invention,preparation of the polyalkylene resins discussed herein and a method ofblending the polyphosphonate or p01y(phosphonate-phosphate).

EXAMPLE I 1200 grams of dimethylterephthalate and 800 grams of1,4-butanediol are mixed together along with an appropriate catalyst asdescribed in the Whinfield and Dickson patent, US. 2,465,319, such aszine acetate-antimony trioxide or lead oxide-zinc oxide. The temperatureis increased to approximately 200 C. when 80 percent by weight of themethanol has been removed. Vacuum is applied and the temperature israised to 240-250 C. When the intrinsic viscosity has reached 0.65 to0.70 dl./g., vacuum is broken and 150 grams of polyfm-phenylencphenylphosphonate) are added under nitrogen. The mass is then mixed for5 to minutes and the resultant polymer discharged and chipped in theusual manner.

The chips which have an intrinsic viscosity of 0.70 dl./ gm. wereblended with an amount of Ms inch glass fibers, equal to 30% of theirweight, tumble blended for 1 minute melting the polybutyleneterephthalate and then extrusion blended by force feeding through a oneinch single screw extruder with a strand die. The temperatures of theextruder and die ranged from 500 to 510 F. The strands were ground in amilling type mixer to pass through a large screen (4 mesh or smaller).

EXAMPLE II Example I was repeated, but the amount of poly(m- 8 EXAMPLEIII The products of Examples I and II were tested for flame retardancein accordance with Underwriters Laboratories Test No. 94. The resinswere first molded into bars 0.5 x Ms x 6". Then they were positionedvertically over a Fischer burner at a distance of The flame causedimmediate ignition and was held for 10.0 seconds before being removed.

The results are summarized in the following table:

TABLE I Burning rate Sample Control (no polyphosphonate):

a }2.3/min; dripped flaming particles and b. not self-extinguish.

The differences in results for the samples of each example are due toinadequate mixing of the polyphosphonate with the polyester; therebyshowing that intimate mixing is a necessity.

EXAMPLE IV When Examples I and H are duplicated with the substitution ofa copolymer of the average formula poly[(mphenylene phenylphosphonate)][(m-phenylene phenylphosphate)] for poly(m-phenylene phenylphosphonate)and the resultant molding compositions are tested by the procedure ofExample III, the results are similar to the results in Example III.

EXAMPLE V The limiting oxygen index is a relatively recent procedure forevaluating the flammability of polymeric materials [C. P. Fenimore andF. J. Martin, Combustion and Fla-me, 10, (1966); C. P. Fenimore and G.W. Jones, Combustion and Flame, 10, 295 (1966); and C. P. Fenimore andF. J. Martin, Modern Plastics, 43, 141 (1966)]. The procedure basicallyconsists of measuring the minimum percentage of oxygen in anoxygen-nitrogen atmos phere capable of sustaining a candle-like flame onthe top of a vertically mounted sample. This limiting or minimumpercentage of oxygen guarantees total consumption ofdthe sample and isreferred to as the limiting oxygen in ex.

The oxygen index apparatus is comprised of a glass combustion chamberand means for introducing an oxygen-nitrogen mixture at a known rate offlow, the composition of which mixture may be varied and monitoredcontinuously. The combustion chamber consists of a sample holder whichis centrally located and oxyhydrogen microfiame located adjacent to thesample holder. The lower portion of the combustion chamber containsglass beads to a depth of about 12 inches in order to insure a uniformgas flow of about 3 cm. sec.

Samples for use in the oxygen index apparatus are prepared by pouringpowdered polymer into a Teflon tube, which is /2 inch in diameter andclosed at the bottom, mounted vertically in a heated aluminum block. Thepolymer powder is poured into the Teflon tube under a nitrogen purge,gently packed, and heated to 285 C. After 5 minutes the tube iswithdrawn, allowed to cool, and the Teflon stripped away, leaving apolymer plug.

The sample polymer plug is supported vertically in the sample holder ofthe combustion chamber and is ignited with the oxy-hydrogen microflame.If a burn is unattainable, the oxygen level is recorded and raised. If asteady,

candle-like flame is obtained, the oxygen concentration is recorded, theflame extinguished, and the procedure repeated at a lower oxygenconcentration. This procedure is followed until the minimumconcentration capable of sustaining a steady-state flame is determinedfrom both directions. Only a centrally-located flame on a flathorizontal surface is conclusive. The minimum oxygen concentration thusdetermined is the limiting oxygen index.

The experimental data and limiting oxygen indices (L.O.I.) for samplesof resins from Examples I and II are given in the following Table II:

carbon atoms selected from the group consisting of alkoxy, aryloxy,hydroxy, haloalkoxy, haloaryloxy, hydroxyalkoxy, and hydroxyaryloxy; Ris a monovalent radical having up to 20 carbon atoms and isindependently selected from the group consisting of hydrogen, alkyl,aryl, haloalkyl and haloaryl; R is a monovalent radical having up to 20carbon atoms and selected from the group consisting of alkyl, aryl,haloalkyl, and haloaryl; Ar and Ar are divalent radicals each having upto about 20 carbon atoms independently selected from the groupconsisting of arylene and haloarylene; Z is a divalent TABLE II IgnitionTrial Percent Ignition Position Flame Burn Flame Bar Sample No. 0 cone.time time type type out consumed L.O.I.

1 26.0 Immediate 30 seconds..- M Even- 4/5.0 100% Example 1.... 2 27.0-..do -.do M ..-do 3/11. 100% 27.2

0.- Example 11... 2 do. 3/2 27:} 52 Control 1 do a/e 2% i" 21.0

Norm-Similar results are obtained with glass reinforced resin.

EXAMPLE VT Dime-thyl terephthalate (58 parts), 1,4-butanediol (38.6 25

parts), and 0.06 part of the reaction product of tetraisopropyl titanatewith diphenyl silanediol in a mole ratio of 2:1 are charged to anautoclave and heated to 150 C. Methanol is distilled. The distillationof methanol is taken to 80 percent completion while the autoclavetemperature is increased to 225 C. 'Polycondensation then isaccomplished at 250 255 C. and at a pressure of 0.1-1.0 mm. Hg. Thevacuum is released under a nitrogen purge and the autoclave charged with0.06 part of triphenyl phosphite and 2.9 parts of poly(m-phenylenephenylphosphonate). The resultant mixture is stirred under the nitrogenatmosphere to provide good dispersion of the polyphosphonate in the meltand the resultant mixture extruded. The resultant polyester compositionhas a relative viscosity of as determined in o-chloropheno'l at 25 C.and a melting point of 222 C. as determined by differential scanningcalorimetry. The polymer has a limiting oxygen index of 27.4. Similarresults are obtained with glass reinforced resin.

EXAMPLE VII The procedure of Example V1 is repeated, except that thepoly(m-phenylene phenylphosphonate) is omitted. The result-ant polyesterhas a limiting oxygen index of 25.2.

EXAMPLE VIII When the previous Examples are repeated with the exceptionthat polypropylene terephthalate is substituted for polybntyleneterephthalate, the flame retarding results are similar.

Having thus disclosed the invention, what is claimed is:

'1. Phosphorus-containing reinforced polyester molding resincompositions having a limiting oxygen index of more than about 26comprising blends of from about 2 to about 60 weight percent of areinforcing agent, based on the total weight of .the composition, asynthetic linear polyalkylene terephthalate selected from the groupconsisting of polypropylene terephthalate and polybutyleneterephthalate, the polyalkylene terephthalate having an intrinsicviscosity in the range of from about 0.2 to about 1.2 deciliters pergram, and up to about 30 weight percent, based on the weight of thepolyalkylene terephthalate, of a polyphosphonate or apoly(phosphonate-phosphate) copolymer having the following generalformula:

it. .111... .U.

wherein R is a monovalent radical having up to about radical selectedfrom the group consisting of oxy and thio; Z is either hydrogen or q isan integer of at least 1; r is an integer of 0 or at least 1; and x isan integer which is greater than 1.

2. The phosphorus-containing polyester compositions of claim 1 whereinsaid synthetic linear poly-alkylene terephthalate is polybutyleneterephthalate.

3. 'Poly(butylene) terephthalate polymer compositions of claim 2comprising a flame retarding amount up to about 25 percent by weight ofa poly-(phenylene-phenylphosp'honate) 4. The phosphorus-containingpolyester compositions of claim 3 wherein thepoly(phenylene-phenylphosphonate) is incorporated in the range of fromabout 3 weight percent to about 15 weight percent.

5. The phosphorus-containing polyester composition of claim 2 whereinthere is present poly[(m phenylene phenylphosphonate) -(m phenylenephenylphospha-te) said copolymer being incorporated in the range of fromabout 3 weight percent to about 15 weight percent, and where q/ r has avalue greater than 2.

References Cited UNITED STATES PATENTS 2,435,252 2/1948 Fon Toy 260-472,968,639 1/1961 Caldwell et al. 260-33.'8 3,027,349 3/ 1962 Bahr et al.260-45.7 3,169,925 2/ 1965 Mahoney 252-498 3,356,631 12/1967 Jackson,Jr. et al. 260-31.2 3,406,224 10/ 1968 McDonough 260-8'60 3,516,9576/1970 Gray, Jr. et al. 260-22 3,535,300 10/1970 Gable 26029.1 3,546,17912/1970 Koller 260-75 3,562,220 '2/ 1971 Jones et al 260-40 3,575,9314/1971 Sherman 260-75 2,636,876 4/ 1953 Zenitrnan et a1 260-47 2,964,47712/1960 Pilat et al. 252-498 3,624,024 11/1971 Caldwell et al. 260-40OTHER REFERENCES Kosolapoff: Organophosphorus Compounds, 1950, pp. 241and 243.

DONALD E. CZAJA, Primary Examiner R. A. WHITE, Assistant Examiner US.Cl. X.R.

260-45.7 'P, 45.95 D, 45.95 P, 75 P, 860

